Method of converting standard threads into locking threads



Fi l e d S e p t 3 O 1 9 52 SAN 2,787,796 G STANDARD THREADS NG THREADS 2 Sheets Sheet 2 /yl Q .a9

'ofthe threads, and withoutc'ontributi METHOD OF CONVERTING STANDARDVTHREADS [NTO LOCKING THREADS Joseph Rosan, Newport Beach, Calif. Application September `30, 1952, Serial No.y 312,231 4 ClamS. (Cl.l 10-8 `6)' This invention relates toscrewthreadsgfiandmore-par? ticularly, to a method and apparatus'` forfmodifyingor converting either a standard male or, a standard'fernale thread' into a thread'that will'lockl with anunmodified. standard mating thread of vthe corresponding-"diameter and pitch and positively hold theA threadeid' partsd'agfainst loosening 'under extreme conditions -of vibration, temperj aturechangesetc.

i The present invention is related to thersubjectfmatter disclosed in my copendingapplication Serial No.130v99 6l0 filed"v September 17, 1952. Thatf application* discloses "'(finted States Patent. if

specially threaded elements adaptedy tobel used linjlieu of. conventional bolts, nuts, etc.,` and constructedsofth'at when the speciallyy threaded 4element isf screwed qintoy a conventional threaded element, the*threadwoffthejcom ventional element is deformed-in aimannertocause-fit tof be locked to the specially threadedeleiitent.A AIh'lcon'` trast, the present invention yrelatesV to a method andi 'tools for `rriodifying nuts, bolts, etc., havi'ngal standrdthread in' order to producea similailcking Veiecztbetweenv Ya modifiedv standard thread and a co'rrespgondin'g` mating. stndard'thread, whereby to "impartito VIsuch;"standard threaded bolts and nuts the same locking"'propertiesthat a'reattained with a standard threaded 'partand :especially th'readed'part, as'disclosedin said copendingfjapplication; The principal object'ot' the invention" ist'o providea method and tools wherebythread'ed part'swhicharlefnor- Inallyfdevoid of'locking means can be readily modi'ed to' convert the threads-thereof-intopositive" self-locking.- threads "for preventing rotation' of the'l modi hradd part Vwithrespect to either a part provided'with *standard matngthread, or a part having aI standa'rdmtirng; thread which has also been modiedin'accordance* wit` -tlie principles of the invention.` Another object of the'inventionis tomodifytliercrown or'l a conventional thread V'onone'or l'both 'of "ai paiof threadedmembers in suchV aI Ina-nner thttah lock is established between ainenliberhavingfam diiied standard thread anda member' having-iv an unmodified standard thread, o1' between two members-:botti modified standard threads, so `thathetwo parts--can be threadedy together into "locked relationwitliout s up yhigh stressesthat would prodcejgallingonth a ks glft'o' earlylff orffatigue ofthe thread 'members'. l

This, is accomplishedv yby' enlarging-. or, expanding the f crestor crownof the vstand'ardthread)lt 'aneiit gieattjir than the l.normal 'thread clearance,.forthatparticillargtype of thread; in order toefvect interferinglockin engagement of'the modified thread t with -a standard onisirnilarlyfmodi iiedthread. The interferingengagementtandgthei con;l

sequent force or'torque requiredfv-,tofunthread th mem? @rsf-Can heralded-by. `alter-ine thegsharacte a., of: distortion *of the. thread,- crow-n; Thattfisft varying the. extent, to which: the vtiidthf.;and! otithe crown fislgincreased..beyondzits;originalldimensions; When the standard threads on both members are modied,

- compriselamAmericarr National, .ClassfB-thread'; cdi-"iconal 2,787,796 eteetedi-et-f 9s? 1.9.5.2

theglockingjetect is obviously much greaterthanwhen onlyv one thread is modiiied.'

` Anotherlobiect "off the invention is to provide tools-for deforming the'crown` of male and femal threads by im pressing a groove in the crown substantially medially-of the` crown to thereby displace the metal'at thej crown to widen the vcrown beyond its normal width and/or increase thediameter of the crown beyond itsnormal size, whereby the enlarged portions of the crown can friction., ally engage with the anks and/or root of a mating thread to lloc'kthethreads together. In thefcase of'a female thread,``the l thread thereof is modified by the simple expedient yof` threading'a-tool into the femalothread whichE is" specially designed to displacemetalv in a de sire'dvniahner lat the crown of the female thread, without cuttingv metal fiom theA crown.

vAf-further 'object of the invention is to increase the.

utilityA of' members already in existence and provided withlconventional lthreads by modifying they threads of one or--bothof a 4pair of members having mating .threads in` order Vto kprovide' a'positive locking action betweenlthe threads not'lobtainable with the` threads in theirinitiatl` conventional form. i

While ther'invention inits Vbroader aspects vmay be em@ pIoyedLWithanyone of aYK large number ofstandardor conventionalthreadv forms, the; present invention will be described in vconnectioniwith an .American National thread of well-known, conventonal`form'.= Such.. threads arezVf shaped with a included angle between. thetanks, of adjacent threads, and in Class 3 threadsin thisv systemv the dimensional tolerancesare such that the flanks ofthe matingthreads mayhave clearance, butnotinterference: Alsogthecrownszor crests of the mate and female threads are truncated. The modified thread of the present inverntioniis obtained bydeforrning the crowns, of the1conventionaltruncatedsurface, to provide interference.,ad?y jacent thezvrootof the mating thread. The principlesrof the invention are.. equally applicable toVv parts; formed Yof either :ferrous: or; nonaferrous metals, -forl example;V steel andaluminum alloys.

Otheriobjectszand features `of .the invention. Vwill be; aps parent from fthe following descriptiontaken inconjnno tion with the accompanying.V drawings, in which;

Fig. l is a; sectional view showing a ragmenhofa memberfprovidedwith a standard female threadandm fragment-of.; al toolv for deforming., the crown of such femalethread;

Fig.'V g2-is avilew 'oi-the. complete tool; I

Eig- 3 isJan eniargd fragmentary Ysectional viewfof the modiiiedqfemale.threadV tif-Fig l mounted upon a member htlvinga .standard malev thread of .correspendingv size;

Eig,y 4 is a viewpartlyin section but showing, in elevation, a' standard boit extending. through tivo partsand havingfatmoditied ynut threaded thereon forseenringgsaid two partstogether;

Fig. Sfisanrenlarged view'illustratingthe :nalethread kymodifiedmale'threadi ofFig'. 5' inoperative relationft'o ai: standardfemale threadv of v corresponding size.

notl'lrti-is -shownprovidedwith a standard: or: conventional inter-nait thread. il, and; as f-illustrated, thi 'slthreadf' i may.

ventional V-shaped configuration. It will be understood that the thread 11 could be present in a hole or opening in any member, and that the nut 16 has been shown merely by way of illustration and not limitation. The thread 11 has flanks 12 and 13 with a 60 included angle therebetween, the crown 14 being truncated and normally having a smooth cylindrical surface. Since the thread 11 is conventional, it would not ordinarily positively, lockingly engage with a standard bolt, stud, etc. having threads of a corresponding diameter and pitch. Therefore, in order to impart locking properties to the thread 11, the crown 14 is modified according to the present invention to increase its width and/or diameter by a hard, smoothly ground and burnished tool 16, a fragment only of which is shown in Fig. l.

The complete tool 16 is shown in Fig. 2 and comprises a shank 17 having a passageway 1S extending therethrough and a bar 19 disposed in the passageway 18 to facilitate turning of the tool manually. The tool 16 fur ther comprises a generally cylindrical portion, of a suitable length and a diameter larger than the shank 17, provided with a main helical thread 20 on the exterior thereof, the thread 20 having a diameter and pitch corresponding to that of the thread 11. However, the root of the thread 20, instead of being cylindrical and plain, has a second thread or ridge 21 formed between the convolutions of the main thread 20. The ridge 21 is symmetrical in cross section and is rounded at its crest, as best shown in Fig. 1. The ridge 21 is further characterized by the presence of arcuate fillets 22 formed on either side of the ridge 21 and serving to merge the ridge with the adjacent flanks 23 and 24 of the main thread 20. The thread 20 has a plain crown 25 and the flanks 23 and 24 are relieved inwardly of the crown so that the included angle between the flanks 23 and 24 is about 50. The relieving of the anks 23 and 24 and the provision of the fillets 22 provides the clearance space necessary to receive the metal displaced from the crown 14 of the thread 11 when the tool 16 is threaded into the nut 10 to perform the modifying operation on the thread 11. The height of the ridge 21 may be varied so that the height of the thread 11 is about 31/2 to 7 times the height of the ridge 21, depending upon the extent of deformation to be imparted to the thread 11 to provide a given resistance to rotation.

As a specific example, a diameter standard nut and bolt has 16 threads to the inch, and a clearance of about .00075 of an inch between the confronting flanks of the mating threads, or a total clearance of .0015 of an inch for each thread. In order to provide a positive lock, the crown of the thread 11 is distorted or expanded to an amount equal to about twice the total normal clearance, or about .003 of an inch. This provides a total excess of .0015 of an inch of metal on the threads 11 to bind or be displaced back toward normal in effecting the lock. The same principle of distorting the thread to twice the total normal clearance applies also to the root clearance, in instances Where locking engagement between the periphery of the crown of the thread 11 and the root of the mating thread is desired. The ridge 21 and the fillets 22 may be varied in shape and/or size to provide the desired flank and/or root interference.

As the tool 16 is threaded into the nut 10, the main thread 20 thereof engages with the thread 11 to feed the tool through the nut. As the tool 16 is rotated, the ridge 21 is forced into the medial portion of the crown 14 exerting pressure in a direction perpendicular to the axis of the thread 11, thereby forming a substantially central groove 26 in the crown and displacing the metal of the crown laterally in both directions, and also inwardly, to form the rounded or bulbous enlargements 27 and 28, which are localized at either side edge of said crown. The deformation of the crown 14 widens the crown beyond its original dimension and also increases the height of the thread 11 beyond its original height. As previously indicated, the relieved flanks 23 and 24 and the fillets 22 provide the necessary clearance space to accommodate the lateral and radial expansion of the crown represented by the portions 27 and 28. The dot and dash line 29 in Fig. 1 constitutes a projection of the unmodified crown 14 to graphically emphasize the expansion which is effected by the action of the tool 16 on the crown 14.

Fig. 4 shows the nut 10 mounted upon a standard bolt 30 extending through a pair of plates 31 and 32. Fig. 3 shows a fragment of the nut 10 and a fragment of the boit 3f) to an exaggerated scale toy illustrate the manner in which the standard thread 33 of the bolt is locked with the modified thread 11 of the nut. Thus, it will be apparent that an interference fit is provided between the portions 27 and 28 of the modified thread 11 and the adjacent flanks 34 and 35 of the standard thread 33. The distortion which occurs in the crown 14 to provide the portions 27 and 28 is substantially symmetrical, as indicated in Fig. 1, so that as the standard male thread 33 is threaded into the modified female thread 11 and the nut 10 is drawn up tightly, the flank 13 of the female thread engages with the flank 35 of the male thread and the portion 28 tends to be displaced toward the groove 26 and toward the root 36 of the male thread to frictionally engage therewith. The portion 27, on the other hand, frictionally engages the adjacent flank 34 of the male thread 33 so that frictional engagement between the standard male and modified female threads occurs be tween the adjacent flanks of both threads. The clearances are exaggerated in Fig. 3 to facilitate illustration of the principles involved.

The crown 14 may be distorted to an extent to provide an interference fit only with the flanks of the bolt thread, without providing an interference tit with the root, or vice-versa. However, as shown in Fig. 3, the displaced portions 27 and 2S provi-de locking engagement with the flanks 34 and 35 of the bolt 33 and also provide locking engagement with the root 36 of the bolt thread.

The tool 16 is particularly useful for modifying the threads of stud holes in engine blocks or other machine parts, since the tool can be readily threaded into the stud openings without requiring removal of the parts to a special machine. However, if small parts, such as nuts, plates, etc. having holes provided with standard threads, are to be reworked to convert the thread thereof into a locking thread, then the bar 19 can be removed from the tool 16 and the shank thereof mounted in a suitable chuck and the tool power-operated to modify the threads in a manner similar to that of a tap. In addition, the tool 16 can be used to recondition a modified thread that has lost some of its effectiveness through numerous removal and reassembly operations.V

Fig. 5 is an enlarged view illustrating the manner in which the thread 37 of a standard bolt 38 (or any other part) may have the crown thereof modified by a rolling tool 39 having a rounded ridge 40. The bolt 33 is preferably mounted in a lathe (not shown) and the rolling tool mounted on a carriage (not shown), adjusted so that the ridge 40 of the tool 39 engages the central portion of the crown 41 of the thread to apply pressure to the crown in a direction perpendicular to the axis of the thread 37 and thereby form a groove 42 and displaced portions 43 and 44 similar to the groove 26 and displaced portions 27 and 28 formed on the female thread 11. The crown 41 of the bolt thread 37 is thus distorted and adapted to be engaged in the same manner as the modified crown of the thread 11. Here again, the extent of the Idistortion of the bolt thread 37 can be varied depending upon the adjustment of, and the pressure applied by, the rolling tool 39 to vary the width and diameter of the crown of the modified thread. When a standard nut145, only a fragment of which is shown in Fig. 6, is threaded on lthemoditied bolt thread 37, inter ference to rotation is developed between the enlarged portions 43 and 44 of the crown 41 and the flanks 46 and ghi.

d 47 of the nut thread 48 adjacent the root 49 of said nut thread, so Ithat a positive locking action is attained between the two threads 37 and 48 in the same manner described in connection with Fig. 3.

Thus, conventional threaded parts such as the nut and the bolt 38, which normally have no `locking action other than that caused by the friction between the iianks of the conventional threads, can readily be modified by use of the tools 16 and 39 disclose-d herein to alter the threads in a simple manner within the skil'l of even an untrained worker, to impart positive locking characteristics to such parts to enhance their utility and to enable such parts to be used under conditions of vibration, etc., for which they would normally be unsuite-d.

While reference has been made hereinbefore to the use of a part having a standard thread with another part having a corresponding, but modified, standard thread, it is to be understood that male and female threaded parts both having their threads modified in accordance with the principles of the invention may be threaded together to obtain the combined advantage of the locking threads on both the male and female members.

It is to be understood that variations may be made in the contour of the ldeformed threads and in the tools used to form such threads without ldeparting from the principles of the invention or the scope of the annexed claims. v

I claim:

l. The method of converting the thread on a member having a standard thread with a truncated crown into an automatically locking thread cooperable with an unmodiiied mating thread of another member having a standard thread of corresponding size, comprising the step of: applying force to the truncated crown of the thread in a direction transverse to the axis of the thread at a point about medially of the width of the crown to modify the shape of the crown by displacing the metal thereof laterally and radially sutiiciently to increase the width and radial height of the thread at the crown and by an amount greater than the normal clearance that ysaid standard thread would have with an unmodilied standard mating thread, whereby when another threaded member having a corresponding mating standard but unmodified thread is brought into threaded engagement with the modified thread, the expanded portion of the modied thread will frictionally bind against the unmodified thread and lock the threads together.

2. The method of converting a standard thread into a locking thread, as deiined in claim 1, in which the crown of the truncated thread is displaced to increase the width thereof by an amount approximately twice that of the normal clearance for a given size of standard thread.

3. The method of converting a standard thread having anks and a truncated crown on one member, into a locking thread cooperable with an unmodified mating standard thread of corresponding size on another member, comprising the steps of: applying suiiicient radial force to the truncated crown of the thread of said one member at a point intermediate the side edges of said crown to laterally displace the metal of the crown and form bulbous enlargements localized at either side edge of said crown to increase the width of the thread at said crown by an amount greater than the normal clearance for said size of standard thread, while preserving substantially the original shape of the flanks of the thread inwardly of said crown, so that when another member having a corresponding standard unmodified thread is engaged with the modified thread, the enlargements will irictionally bind against the adjacent flanks of the nnmodified thread and lock the members together.

4. The method of converting a standard thread having anks and a truncated crown on one member into a locking thread cooperable wtih an unmodified mating standard thread of corresponding size on another member, comprising the steps of: forming a groove of suicient depth in the truncated crown of the thread of said one member at a point intermediate the side edges of said crown to laterally displace the metal of the crown and form bulbous enlargements localized at either side edge of said crown, to increase the width of the thread at said crown by an amount greater than the normal clearance for 4said size of standard thread, and without decreasing the radial height of said thread at the side edges of said crown, so that when another member having a corresponding standard unmodified thread is engaged with the modified thread, the enlargements wiil frictionaliy bind against the adjacent flanks of the unmodified thread and lock the members together.

References Cited in the tile of this patent UNTEB STATES PATENTS 658,085 Higbee Sept. 18, 1900 793,824 Culliney July 4, 1905 1,369,156 Woodward Feb. 22, 1921 1,451,484 Woodward Apr. 10, 1923 2,109,778 Meersteiner Mar. l, 1938 2,177,100 Frome Oct. 24, 1939 2,301,679 Bouget Nov. 10, 'i942 2,354,810 Haas Ang. 1, 1944 2,371,365 Tomalis et al. Mar. 13, 1945 2,429,832 Luce Oct. 28, 1947 2,454,444 Poupitch Nov. 23, 1.948 2,556,174 Evans June 12, 1951 2,581,690 Moeh-le Jan. 8, 1952 

